So yeah, this is shorter $_ //= '' for values %foo; than $foo{$_} //= '' for keys %foo;, and sure, you can say its more DRY, but DRY doesn't care about it, its the same one line talking about the same one variable %foo, nothing that can get out of whack because of any duplication
Actually, it can easily get out of whack: 
$foob{$_} //= '' for keys %foo;

[download]
Now the maintenance programmer must ask: is this really the intent ... or is it a typo?

Using the name once only makes the intent clearer, that is: 

$_ //= '' for values %number_of_immortal_perl_monks

[download]
makes it clear, at a glance, that the intent is to update a single hash, while: 
$number_of_immoral_perl_monks{$_} //= '' for keys %number_of_immortal_
+perl_monks

[download]
gives the maintenance programmer a headache.

Finally, with: 

$foo{$_} //= '' for keys %foo;

[download]
to rename the foo hash to a better name you must change it in two places, rather than one, so there is (an admittedly small) chance of error when you are doing search-and-replace in your editor (code refactoring IDEs help here).

In reply to Re^5: Convert undef to empty string in a hash by eyepopslikeamosquito
in thread Convert undef to empty string in a hash by ibm1620

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.